MCDANIEL TANK RHYOLITE

The McDaniel Tank Rhyolite obsidian source, discovered by Jeff Ferguson (Missouri Research Reactor Center), is part of the Squaw Peak Volcanic Center, identified and described by Bobrow (1983; see also Bobrow et al. 1983). The Squaw Peak Center is in the far northeastern portion of the Mogollon-Datil Volcanic Province dated between about 35 and 20 Ma (Shackley et al. 2017).  The Squaw Peak Volcanic center is comprised of three distinct mid-to-late Tertiary (Neogene) rhyolite domes, the oldest is the flow banded phenocryst poor, high-K, high SiO₂ rhyolite tephra that covers much of the northern part of Squaw Peak and north that includes McDaniel Tank dated by K-Ar to 18.3 ± 0.7 Ma (Bobrow 1983:15; see image below). More recently a ⁴⁰Ar/³⁹Ar date was obtained on the obsidian at 14.61±0.01 Ma (Peters 2020).  The tuff is characterized as a dark brown to black, welded, basal ash flow tuff overlain, in parts, by a folded lithoidal lava. Obsidian was not recorded by Bobrow.  The marekanites appear to be lava fragments quenched during the ash flow eruptive event. Field survey during August of 2012 indicated outcrops of marekanite clusters at various points in the 4.1 km³ tuff volume, although the distribution of the ash flow seems larger than that recorded by Bobrow (Bobrow 1983:15). While the volume is relatively low, the area covered is quite large given the relatively thin depth of the ash flow as seen in 2012.

Analysis by XRF and NAA by Bobrow (1983) indicates a relatively close similarity between the major, minor, and trace elements between his sample of rhyolite lava and the obsidian given the expected differences between a crystalline rhyolite and glass (see Bobrow et al. 1983:215). 

One projectile point produced from McDaniel Tank obsidian was recovered from one of the sites at Chaco Canyon, and one piece of debitage from the Late Paleoindian levels at Water Canyon near Socorro was recovered (Moss et al. 2023; Shackley 2024).  That's the only appearance of this source in any projects from this laboratory.

Table 1.  Elemental concentrations for the McDaniel Tank Rhyolite obsidian source standards, mean values for Bobrow et al. (1983) rhyolite analysis, and USGS RGM-1 rhyolite standard.  All measurements in parts per million (ppm). n.r.=no report

Table 2. Mean and central tendency for the data in Table 1.

Table 3.  Major and minor oxides for one sample of McDaniel Tank obsidian, Bobrow et al. (1983) analysis of a McDaniel Tank rhyolite sample, and USGS RGM-1 rhyolite standard.

¹ FeO 

Figure 1.  The northeastern Mogollon-Datil Volcanic Province volcanic centers (from Bobrow 1984)

REFERENCES

Bobrow, D.J. 1984, Geochemistry and petrology of Miocene silicic lavas in the Socorro-Magdalena area of New Mexico.  Master's thesis, Department of Geology, New Mexico Institute of Mining and Technology, Socorro.

Bobrow, D.J., P.R. Kyle, and G.R. Osburn, 1983, Miocene rhyolitic volcanism in the Socorro Area of New Mexico.  In C.E. Chapin (Ed.) Socorro Region II, New Mexico Geological Society 34th Annual Field Conference, pp. 211-218. New Mexico Institute of Mining and Technology, Socorro.

Moss, J.M., Windes, T.C., A.I. Duff, W. Doleman, and M.S. Shackley, 2023, A diachronic analysis of obsidian use at Chaco Canyon and the influence on social factors on obsidian procurement. Kiva 89:370-402.

Peters, L. 2020. 40Ar/39Ar geochronology results from the Mogollon-Datil Province obsidian study.  Report # NMGRL-IR-Shackley1182, New Mexico Institute of Mining and Technology, Socorro.

Shackley, M.S. 2024, Obsidian sources and source provenance of archaeological obsidian in northern Sonora: the known and unknown. In Kiva Special Issue: H. Claypatch and E. Villalpando Canchola (Eds.) Reframing and Expanding Sonoran Archaeology, Kiva 90:293-305.

Shackley, M.S., L.E. Morgan, and D. Pyle, 2019, Elemental, isotopic, and geochronological variability in Mogollon-Datil Volcanic Province archaeological obsidian, Southwestern New Mexico: solving issues of inter-source discrimination.  Geoarchaeology 33:486-497.

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